JP2003282995A - Magnetic field detecting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic field detecting element wherein an element can be manufactured which has a characteristic that a part whose element impedance characteristic is reduced monotonously to an external magnetic field appears on a low magnetic field side, and an element having a wide measurement region can be manufactured without largely increasing an element driving consumption power by using the part for measuring a magnetic field. <P>SOLUTION: In the magnetic field detecting element 11, an AC current is supplied from a high frequency power source 18 to a thin film magnetic member 13, and change of electric characteristic which corresponds to external magnetic field is detected. By using the electric characteristic that impedance is reduced corresponding to increase of absolute value of the external magnetic field, magnetic field is detected. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic field detection element, and more particularly to a high linearity / low bias type magnetic impedance type magnetic field detection element.

[0002]

2. Description of the Related Art With the recent rapid development of information equipment and measurement / control equipment, the demand for a compact, low-cost, high-sensitivity / high-speed response magnetic sensor is increasing. For example, in a hard disk device of an external storage device of a computer, performance has been improved from a bulk type induction type magnetic head to a thin film magnetic head and a magnetoresistive (MR) head.

Further, in a rotary encoder which is a rotation sensor of a motor, the number of magnetic poles of a magnet ring is increased, and a weaker surface magnetic flux can be detected with high sensitivity in place of a magnetoresistive effect (MR) sensor which has been conventionally used. Magnetic sensors are needed.

There is also an increasing demand for high-sensitivity magnetic sensors that can be used for nondestructive inspection, bill inspection, and biomagnetic field measurement.

Inductive reproducing magnetic heads and magnetoresistive effects (MR) are used as typical magnetic detecting elements currently used.
There are elements, fluxgate sensors, Hall elements, etc.

Further, recently, a highly sensitive magnetic sensor utilizing the magnetic impedance effect of an amorphous wire has been proposed (JP-A-6-176930 and JP-A-7).
-181239 gazette and Unexamined-Japanese-Patent No. 7-333305 reference).

A high-sensitivity magnetic sensor utilizing the magnetic impedance effect of a magnetic thin film has also been proposed (Japanese Patent Laid-Open No. 8-75835, Journal of Japan Society for Applied Magnetics, vol.
20, 553 (1996)).

Since the induction type reproducing magnetic head requires a coil winding, the magnetic head itself becomes large. Moreover, if the relative speed between the magnetic head and the medium is low,
There is a problem that the detection sensitivity is significantly reduced. On the other hand, a magnetoresistive (MR) element using a ferromagnetic film detects the magnetic flux itself, not the time change of the magnetic flux, and thus miniaturization of the magnetic head has been promoted.

However, the current MR element has a change rate of electric resistance of about 2%, and even an MR element using a spin valve element has a small change rate of 6% or less at maximum. Also,
The external magnetic field required to obtain a resistance change of several percent is 1600
Greater than A / m. Therefore, the magnetoresistive sensitivity is 0.00
Low sensitivity of 1% / (A / m) or less.

Further, recently, the rate of change in magnetic resistance is several tens of percent.
The giant magnetoresistive effect (GMR) due to the artificial lattice showing is shown. However, an external magnetic field of tens of thousands A / m is required to obtain a resistance change of tens of percent.

A fluxgate sensor, which is a conventional high-sensitivity magnetic sensor, measures magnetism by utilizing the fact that the symmetrical BH characteristics of a high-permeability magnetic core such as ferrite and permalloy are changed by an external magnetic field. It has high resolution and high directivity of ± 1 °. However, in order to increase the detection sensitivity, a large magnetic core is required, which makes it difficult to reduce the size of the entire sensor and further has a problem that the power consumption is large.

In a magnetic field sensor using a Hall element, when a magnetic field is applied perpendicularly to the surface through which a current flows, an electric field is generated in a direction perpendicular to both the current and the applied magnetic field, and an electromotive force is induced in the Hall element. It is a sensor that utilizes the phenomenon of The Hall element is advantageous in cost, but has low magnetic field detection sensitivity. Further, since it is composed of a semiconductor such as Si or GaAs, the mobility of electrons or holes changes due to the thermal vibration of the lattice in the semiconductor with respect to the temperature change, so that the temperature characteristic of magnetic field sensitivity is poor. Has the drawback.

On the other hand, JP-A-6-176930, JP-A-7-181239 and JP-A-7-333305.
As described in the publication, a magneto-impedance element has been proposed to realize a significant improvement in magnetic field sensitivity.
This magneto-impedance element is a magneto-impedance element whose basic principle is to detect only a voltage as a change due to an externally applied magnetic field with respect to a time change of a circumferential magnetic flux generated by applying a time-varying current to a magnetic wire. Is.

As this magnetic wire, (FeCoSiB), etc.,
An amorphous wire with a zero magnetostriction diameter of about 30 μm (a wire that has been tension-annealed after being drawn) is used. Even a minute wire with a length of about 1 mm, when a high-frequency current of about 1 MHz is applied, the voltage amplitude of the wire is increased. However, it changes at a high sensitivity of about 100% / Oe, which is 1000 times or more that of the MR element.

The thin-film magneto-impedance elements described in JP-A-8-320362 and JP-A-11-109006 are thin film structures containing a magnetic material on a substrate by a sputtering method or a plating method. A magnetic impedance effect is obtained by forming a body and passing a high frequency current through it.

[0016]

In the conventional thin-film magneto-impedance element, the magnetic field (bias magnetic field) that must be applied from the outside in order to maintain the operating point of the element is large, the electric circuit design is complicated, and the element is complicated. There was a disadvantage that the power consumption required for driving was large.

Therefore, an object of the present invention is to manufacture an element having a characteristic that the portion of the element impedance characteristic that monotonously decreases with respect to the external magnetic field appears on the low magnetic field side. An object of the present invention is to provide a magnetic field detection element that can be used for measurement to manufacture an element having a wide measurement region without significantly increasing element driving power consumption.

Another technical problem of the present invention is
It is an object of the present invention to provide a magnetic field detection element capable of ensuring a wide linear region in a measurement region that monotonically decreases with respect to an external magnetic field and capable of performing highly accurate measurement in a wide magnetic field region without a feedback circuit.

Still another technical problem of the present invention is to provide a magnetic field detecting element which can increase element impedance and reduce driving power because it is a thin wire element, which is effective for downsizing of the apparatus. Especially.

[0020]

The magnetic field detecting element of the present invention overcomes the above disadvantages of the thin film magneto-impedance element.

Specifically, the region where the element impedance decreases with an increase in the external magnetic field, which is the magnetic field detection region, is
We have realized a new element that does not exist in the past, that is generated in a magnetic field lower than the bias magnetic field of the conventional element, and reduced the power consumption required to drive the element compared to the conventional element.

Further, since the element brings about a wide detection range, it is possible to realize magnetic field detection with good linearity without correction by a complicated electric circuit.

In order to solve the above problems, the present invention provides
(1) In a magnetic field detection element that supplies a thin film magnetic body with an alternating current from a high frequency power source and detects a change in electrical characteristics according to an external magnetic field, with respect to an increase in the absolute value of the external magnetic field,
It is characterized by being a magnetic field detection element that detects a magnetic field by utilizing the electrical characteristics of which impedance decreases.

Further, in the present invention, (2) in the thin-film magnetic material according to (1) above, among the domain walls that appear due to the domain structure, the domain walls other than the domain wall generated by the reflux domain are tilted with respect to the energization direction. Therefore, the impedance of the external magnetic field is reduced from zero when the absolute value of the external magnetic field is increased.

Further, in the present invention, (3) in the thin-film magnetic material described in (1) or (2) above, among the domain walls developed by the domain structure, a domain wall other than the domain wall in which the reflux domain is generated, and a current direction It is characterized in that the small angle side of the angle formed by is 0 ° or more and 30 ° or less.

Further, in the present invention, (4) the above (1),
The thin film magnetic material according to (2) or (3) has an aspect ratio defined by the long side / short side of the element cross section perpendicular to the energization direction,
By defining the width, film thickness, and length of the element to predetermined values, it is characterized by exhibiting electrical characteristics that the impedance decreases from zero external magnetic field with respect to an increase in the absolute value of the external magnetic field.

Further, in the present invention, (5) above (1),
In the thin film magnetic material described in (2), (3) or (4), the aspect ratio of the element cross section perpendicular to the current flowing direction of the magnetic thin film is 3
8 or more, the width of the magnetic thin film is 5 μm or more and 15 μm or less, the thickness of the magnetic thin film is 1.5 μm or more and 3.5 μm or less, and the length of the magnetic thin film is 0.5 mm or more and 3 mm or less. Is characterized by.

In the present invention, (6) the above (1),
In the thin film magnetic body according to (2), (3), (4) or (5), the frequency of the alternating current supplied from the high frequency power source is 10 MHz or more and 300 MHz or less when detecting the external magnetic field. It has a feature.

Further, in the present invention, (7) above (1),
The thin film magnetic material according to (2), (3), (4), (5) or (6) is a thin film magnetic material composed of a single-layer magnetic material, or alternating magnetic material and non-magnetic material. It is characterized in that it is a laminated thin film magnetic body.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

First, the principle of the present invention will be described.

In this case, the sensor element has a longitudinal direction in which a high-frequency current is applied and a width direction in a direction orthogonal thereto.
The magnetic substance is excited by a high-frequency current that is conducted. What is important here is the high-frequency magnetic permeability in the width direction, which is the direction of the magnetic field in which the conduction current is generated. A phenomenon in which the high-frequency permeability in the width direction of the thin film changes due to an external magnetic field is called a bias magnetization phenomenon. In this case, the impedance of the sensor element greatly changes according to the external magnetic field. When a magnetic thin film type magneto-impedance element is constructed, this characteristic is realized by giving magnetic anisotropy in a direction different from the external magnetic field to be detected in order to generate this bias magnetization phenomenon. However, in this case, the bias magnetic field, which is the operating point of the sensor element, is defined by the anisotropic magnetic field Hk peculiar to the element material, and when a material having a large Hk is used, a low bias element similar to an amorphous wire is realized. It was difficult.

In the present invention, in the magnetic thin film, the inclination of the magnetic domain is set to an arbitrary angle that does not match the current-carrying direction, or the aspect ratio of the element cross section perpendicular to the current-carrying direction and the width, thickness and length of the element. Is limited to a predetermined value,
We have realized high linearity and low bias magnetic field in a magneto-impedance element whose impedance decreases from zero external magnetic field to the increase of the absolute value of external magnetic field. The conditions are as in the claims.

The present invention is effective even at a driving frequency of about 10 MHz and can be applied to a wide range of purposes.

FIG. 1 is a diagram showing a magnetic domain structure of a magnetic field detecting element according to an embodiment of the present invention. In this figure, 1
Is a thin film magnetic element, 2 is a magnetic domain, 3 is a magnetic domain wall, 4 is a free-flowing magnetic domain, 5 is an energizing direction, and θ is an angle between the domain wall 3 and the energizing direction 5. In this way, the domain wall 3 generated by the reflux magnetic domain 4 generated at the end of the thin film magnetic element 1 is omitted, and the domain wall 3 on the thin film surface is omitted.
Is smaller than the energizing direction 5 by 0 ° or more 3
By setting the angle to 0 ° or less, it is possible to reduce the bias magnetic field serving as the operating point of the element, at the same time widen the linear region, reduce power consumption for driving the element, and realize a magnetic field detection element with a wide detectable magnetic field region.

In addition to the magnetic single layer structure described above,
It is also possible to have a structure in which magnetic bodies and non-magnetic bodies are alternately laminated.

FIG. 2 is a schematic diagram of a magnetic field detecting element according to an embodiment of the present invention. FIG. 2 (a) is a perspective view thereof, and FIG. 2 (b) is AA of FIG. 2 (a). It is a cross-sectional view, w represents the width of the magnetic film, and t represents the thickness (film thickness), respectively.

In these figures, 11 is a magnetic field detecting element, 12 is a substrate (eg glass), 13 is a magnetic film formed on the substrate 12, or a laminated film consisting of a magnetic film and a non-magnetic film, 14 Is carrier current, 15 is external magnetic field H
ext, 16 and 17 are electrode pads provided at both ends of 13, and 18 is a high frequency power source.

Next, a specific example of the present invention will be described.

(Example 1) The magnetic material composition of the magnetic field detecting element is Co ₈₅ Nb ₁₂ Zr ₃ and R in an Ar atmosphere is used.
The film was formed on the glass substrate by the F sputtering method, and then patterned by the lift-off method. Further, patterning by the ion milling method is also possible. After the film formation, the magnetic film was heat-treated in a magnetic field to impart magnetic anisotropy in the element width direction. The heat treatment conditions in a magnetic field are heat treatment in a rotating magnetic field (40 kA / m, 400
Heat treatment in static magnetic field (40kA / m, 400)
C, 1 hour). The magnetic field detection characteristics of the element were evaluated by measuring the impedance change when the external magnetic field Hext was applied by the Helmholtz coil. Impedance measurement is performed using a network analyzer (eg HP439
6B) was carried out by the reflection method.

In FIG. 3, the dimensions are 2 mm in length and 3.0 in film thickness.
The magnetic-impedance characteristics (absolute value) of the magnetic field detection element having a width of 25 μm and a width of 25 μm are shown. Carrier frequency is 90M
Hz. A region in which the impedance changes linearly with respect to a change in the external magnetic field is called a linear change region, and the magnetic field is detected in that region.

Conventionally, a linear change region in which the impedance increases, which is indicated by A in FIG. 3, has been used for magnetic field detection. In the present invention, the linear change region indicated by B in FIG. 3 where the impedance decreases is used for magnetic field detection. The linear change region in which the impedance decreases has the disadvantage that the bias magnetic field is larger than the linear change region in which the impedance increases, but has the advantage of a wider magnetic field range. In the device of FIG. 3, the bias magnetic field is about twice and the linear change region is about three times. Furthermore, by limiting the magnetic field detecting element to the second to seventh aspects, the bias magnetic field can be reduced without narrowing the linear change region.

FIG. 4 shows an external magnetic field Hext (1 × 10 2 A / m) of the magnetic field detecting element according to the embodiment of the present invention.
It is a magnetic-impedance characteristic diagram. The element has a film thickness of 2.0 μm, a length of 2 mm and a width of 10 μm, and a carrier frequency of 90 MHz. The inclination of the domain wall with respect to the energization direction of this element is about 20 °, and within the scope of the claims of the present invention, a magnetic field detecting element having electric characteristics in which impedance decreases from zero external magnetic field is realized.

Compared with the element of FIG. 3, the bias magnetic field is reduced at the same time when the linear change region is expanded.

FIG. 5 shows magnetic-impedance characteristics at a carrier frequency of 90 MHz for an element having the same composition and the same manufacturing method as in FIG. The dimensions of this element are 2 mm in length, 25 μm in width, and 2.5 μm in film thickness. The inclination of the domain wall with respect to the energization direction of this element is about 40 °, which is outside the conditions of the present invention. From FIGS. 4 and 5, it can be seen that the expansion of the linear change region of the impedance and the reduction of the bias magnetic field are effectively realized within the scope of the claims of the present invention.

In order to obtain a wider linear change region, it is more preferable that the angle formed between the domain wall and the energizing direction is 20 ° or less.

Example 2 FIG. 6 shows the same composition as the device of Example 2,
It is a magnetic-impedance characteristic in 90 MHz of carrier frequencies of the element produced on the same conditions. The dimensions of the element are
The length is 2 mm, the width is 15 μm, and the film thickness is 1.5 μm. The length, width, film thickness and carrier frequency are within the scope of the claims of the present invention, but the aspect ratio (= 10) defined by width / film thickness is outside the range. From FIG. 4 and FIG. 6, the expansion of the linear change area of the impedance and the reduction of the bias magnetic field are
It can be seen that the invention is effectively realized within the scope of the claims of the present invention.

If any one of the aspect ratio defined by width / film thickness, the length, width, film thickness and carrier frequency of the device is out of the claimed range, the impedance decreases from zero external magnetic field. It exhibits no electrical characteristics, the linear change region is narrow, and the bias magnetic field is high.

The cross-sectional shape is rectangular, trapezoidal,
Although it can be a kamaboko type or the like, in any case, the characteristics are defined by the maximum value of the width and the maximum value of the film thickness.

(Example 3) 1.0, 1.5, 2.0, 3.0
At each film thickness of μm, the sensor width is 10, 15, 20,
25 μm, sensor length 0.2, 0.5,
A 1 and 2 mm magnetic field detection element was produced in the same manner as in Example 1. The magnetic impedance characteristics of these 80-shaped elements were measured by a reflection method using a network analyzer. As a result, the ten kinds of elements shown in Table 1 realize the expansion of the linear change region and the proposal of the bias magnetic field within the scope of the present invention. In particular, the elements of Samples 2, 3, and 4 in Table 1 below have a linear change region more than the elements of Samples 1, 5 and 10 because the impedance decreases from zero external magnetic field with respect to the absolute value of the external magnetic field. Wide and small bias field.

[0051]

[Table 1]

Table 1 shows the dimensions of the 80-shaped elements that realize the expansion of the linear variation region and the proposal of the bias magnetic field within the scope of the present invention, and the carrier frequencies of 50 MHz and 90 MHz. The linear change region and the bias magnetic field at the time of are shown.

Further, the present invention is not limited to the above-mentioned embodiments, and various modifications can be made within the scope of the present invention, and these modifications are not excluded from the scope of the present invention.

[0054]

As described above, according to the present invention, the following effects can be obtained.

(A) In the magnetic field detecting element utilizing the magnetic impedance effect, the easy axis of magnetic anisotropy is set to the direction perpendicular to the current-carrying direction (width direction) or an arbitrary angle direction that does not match the current-carrying direction, and the current-carrying direction is further set. Element cross-sectional aspect ratio (width / thickness) of 3 or more and 8 or less, magnetic thin film width of 5 μm or more and 15 μm or less, magnetic thin film thickness of 1.5 μm or more and 3.5 μm or less, magnetic thin film Is prepared so that the length is 0.5 mm or more and 3 mm or less. This makes it possible to fabricate an element that has a characteristic that the portion of the element impedance characteristic that decreases monotonically with respect to the external magnetic field appears on the low magnetic field side. It is possible to fabricate an element having a measurement area three times or more wider than the conventional one without significantly increasing the electric power.

(B) It is possible to secure a linear area that is more than twice as wide as the conventional one in the measurement area that monotonously decreases with respect to the external magnetic field, and to perform a highly accurate measurement in a wide magnetic field area without a feedback circuit. To enable.

(C) Since it is a thin wire element, the element impedance can be increased and the driving power can be reduced. It is also effective for downsizing.

[Brief description of drawings]

FIG. 1 is a diagram showing a magnetic domain structure of a magnetic field detecting element according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of a magnetic field detection element according to an embodiment of the present invention.

FIG. 3 is a diagram showing a relationship between an external magnetic field of a magnetic field detection element and impedance.

FIG. 4 is an external magnetic field H of the magnetic field detecting element according to Example 1 of the present invention.
It is a characteristic view of impedance with respect to ext.

FIG. 5 is an external magnetic field He of the magnetic field detection element outside the conditions of the present invention.
It is a characteristic view of impedance with respect to xt.

FIG. 6 is a characteristic diagram of impedance with respect to an external magnetic field Hext of a magnetic field detection element out of the conditions in Example 2 of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 thin film magnetic element 2 magnetic domain 3 domain wall 4 recirculation magnetic domain 5 energization direction θ angle between the domain wall and energization direction 11 magnetic field detection element 12 substrate (eg glass) 13 magnetic film (or laminated layer composed of magnetic material and non-magnetic material) Membrane) 14 Carrier current 15 External magnetic field Hext 16, 17 Electrode pad 18 High frequency power supply

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Norio Nakai             Miyagi, Izumi-ku, Sendai-shi 2-chome 2-chome, Miyagi             Prefectural Industrial Technology Center (72) Inventor Yoshiaki Ikeda             6-7-1, Koriyama, Taihaku-ku, Sendai City, Miyagi Prefecture             Tokin Co., Ltd. (72) Inventor Kenichi Arai             6-14 Minamimachi, Shiogama City, Miyagi Prefecture F term (reference) 2G017 AA01 AC09 AD51 AD63 AD65                       BA03 BA15

Claims (7)

[Claims] 1. A magnetic field detecting element for detecting a change in electrical characteristics according to an external magnetic field by supplying an alternating current to a thin film magnetic body from a high frequency power source, and the impedance of the magnetic field detecting element increases with an increase in the absolute value of the external magnetic field. A magnetic field detecting element, characterized in that it is configured to detect a magnetic field by utilizing a decreasing electrical characteristic. 2. The magnetic field detecting element according to claim 1,
In the thin-film magnetic body, among the domain walls developed by the magnetic domain structure, the domain walls other than the domain wall generated by the reflux domain are inclined with respect to the conduction direction, so that the absolute value of the external magnetic field increases, A magnetic field detection element characterized by exhibiting electrical characteristics in which impedance decreases from zero external magnetic field. 3. The magnetic field detecting element according to claim 1 or 2, wherein in the thin film magnetic body, among the magnetic domain walls developed by a magnetic domain structure, an angle between a magnetic domain wall other than a magnetic domain wall generated by a reflux magnetic domain and an energization direction is defined. A magnetic field detecting element characterized in that the small angle side is 0 ° or more and 30 ° or less. 4. The magnetic field detecting element according to claim 1, wherein the thin-film magnetic material has an aspect ratio defined by a long side / short side of a cross section of the element perpendicular to the energization direction. By defining the width, film thickness and length of the element to predetermined values, it exhibits electrical characteristics that the impedance decreases from zero external magnetic field with respect to an increase in the absolute value of the external magnetic field. Magnetic field detection element. 5. The magnetic field detecting element according to claim 1, wherein the thin film magnetic body has an aspect ratio of a device cross section perpendicular to a current-carrying direction of the magnetic thin film of 3 or more. The width of the magnetic thin film is 5 μm or more and 15 μm or less, the thickness of the magnetic thin film is 1.5 μm or more and 3.5 μm or less, and the length of the magnetic thin film is 0.5 mm or more and 3 mm or less. And magnetic field detection element. 6. The magnetic field detecting element according to claim 1, wherein the thin-film magnetic body has a frequency of an alternating current supplied from a high frequency power source when detecting an external magnetic field. A magnetic field detection element having a frequency of 10 MHz or more and 300 MHz or less. 7. The magnetic field detecting element according to claim 1, wherein the thin film magnetic body is a thin film magnetic body composed of a single-layer magnetic body, or a non-magnetic body. A magnetic field detecting element, which is a thin film magnetic body in which magnetic bodies are alternately laminated.